Atrial fibrillation (AF) is the most common cardiac arrhythmia, affecting millions of patients worldwide, and is a significant cause of morbidity and mortality (Andrade et al., 2014). During normal sinus rhythm, regular electrical impulses travel sequentially from the sinus node (SN) to the right atrium (RA) and then to the left atrium (LA). In AF, electrical propagation is irregular and seemingly chaotic as these electrical impulses travel nonuniformly through the atria resulting in irregular atrial activation. Based on experimental and computational studies, AF can be maintained by rotors, which are rotating or reentrant electrical impulses. For example, it has been hypothesized that human AF is maintained in the heart by a few independent rotors whose periodic impulses breakup remotely in the atria (Vaquero et al., 2008). These rotors represent localized periodic electrical sources from which propagating waves breakup and become more disorganized (Skanes et al., 1998). Ablation of rotors can terminate AF, thereby supporting their role as AF sources (Pandit et al., 2013).
Methods to improve the accuracy of rotor detection may provide therapeutic targets for catheter ablation of AF; thereby improving the success of AF therapy (Ghoraani et al., 2013). However, identifying rotors in patients with AF is quite challenging owing to the complexity and nonstationarity of intracardiac signals. Recently, rotors have been identified using multielectrode basket catheters and phase mapping of unipolar intracardiac electrograms (EGMs) (Narayan et al., 2012). However, this approach has not been reproducible and phase mapping may not be appropriate when signal features become too complex in AF. A more practical approach to rotor detection is to use a circular catheter that conforms to the geometry of a rotor. For instance, a previous study has shown that rotors can be identified in patients with AF using a circular catheter, but the approach requires visual inspection of several hundred bipolar EGMs, which is a tedious process that is not conducive to real-time analysis during AF catheter ablation therapy (Ghoraani et al., 2013).